Create Task and TaskLogEntry. Add proper validation to logged start & end time. Implement starting & stopping functions.
Add API for starting/stopping tasks. Change Tracker API to always return JSON, with code and message if appropiated.
Merge branch 'feature/47520647_start_stop_tasks' into develop
Merge branch 'master' of github.com:amberbit/KarmaTracker

Conflicts:
	app/models/user.rb
	config/routes.rb
	db/schema.rb